At least THAT mystery is solved! The strange balls are human technology.
A lone vehicle returns? Two vehicles and two quad bikes left the Prometheus, and we've seen the shot where one vehicle and the two quad bikes return, but where was the second vehicle? Is this it?
Now for the most amazing shots of this mini trailer! Although its hard to see here, the arrows point to shrapnel bouncing off the Prometheus. The red circle shows the projectile, which looks like a rock? It bounces off the hull and fragments shatter off it. Seems like an odd weapon? Has the Space Jockey ship fired it at the Prometheus?
More shrapnel and the direction the "rock" takes after impacting with the Prometheus. The Space Jockey ship appears to have not moved. The Prometheus is getting closer!
I'm guessing the Space Jockey ship is with-in the planets gravity field? If so why is it in a vertical stance?